1. Field of the Invention
The invention relates to a piston-cylinder unit, in particular a gas spring, and a method for the manufacture of an anticorrosive piston-cylinder unit.
2. Background Art
Gas springs have been known in large numbers for quite a while; they are used in practice for instance as tailgate gas springs in motorcars. The metal casings of gas springs are painted after assembly of the gas spring. The beaded edge of the casing cannot be painted completely in particular in the case of electrostatic enameling so that corrosion problems arise with prolonged use.
It is an object of the invention to embody a piston-cylinder unit that is not susceptible to corrosion.
According to the invention, a piston-cylinder unit, in particular a gas spring, comprises a substantially cylindrical casing with a central longitudinal axis, which has a first end with an edge that is bent inwards, a closed second end, and an inner space that is filled with a working fluid; a guide unit, which is disposed in the casing in the vicinity of the first end and which is supported outwards by the inwardly bent edge; a piston rod, which is coaxial to the central longitudinal axis, which is displaceably passed through the guide unit, and which has a piston on the end of the piston rod that is on the side of the interior space. In such a piston-cylinder unit, the object of the invention is attained by the features which consist in that a plastic sleeve is mounted on the edge of the casing, which has at least a first cuff that enfolds the edge on the outside of the casing; and by a method for the manufacture of an anticorrosive piston-cylinder unit, including the following steps: providing a piston-cylinder unit, which comprises a substantially cylindrical casing with a central longitudinal axis, the casing having a first end with an inwardly bent edge, a closed second end and an inner space that is filled with a working fluid, a guide unit, which is disposed within the casing in the vicinity of the first end and supported outwards by the inwardly bent edge, a piston rod, which is coaxial to the central longitudinal axis and which is displaceably passed through the guide unit and the end of which on the side of the interior space has a piston, and a plastic sleeve, which is mounted on the edge and has an annular first cuff that projects outwards in the axial direction; coating the outside of the casing with an anticorrosive layer; and bending the first cuff so that it enfolds the edge. The gist of the invention resides in that a plastic sleeve with a cuff is fixed to the inwardly bent edge of the casing, enclasping the outer edge of the casing.
Additional features and details of the invention will become apparent from the description of an exemplary embodiment, taken in conjunction with the drawings.